The present invention relates to a zigzag sewing machine having manually operable pattern selecting means for selecting a desired stitch pattern.
In conventional automatic zigzag sewing machines, an operation of the pattern selecting means for selecting a desired stitch pattern to be formed has been necessary at first prior to working of the machine; then, setting of the amplitude regulator and the feed regulator must be performed, in order to determine a zigzag amplitude and a feed amount suitable for forming the selected stitch pattern, with manually operable knobs which are operatively connected to both regulators, respectively.
The amplitude and feed amount suitable for forming the selected stitch pattern are, however, not necessarily constant, but may be variable depending on stitch patterns. The setting of the amplitude regulator and/or feed regulator is cumbersome for sewing machine operators, which often becomes a cause to give an impression to those unskillful in usage of a sewing machine that it is troublesome to handle.
If, besides, a sewing machine is worked when said amplitude regulator or feed regulator is set into an inappropriate condition, it is not merely incapable of forming a stitch pattern of desired shape but also liable to give doubt whether the machine is out of order.
With the object of obviating such shortcomings as much as possible, a type of sewing machine, as stated in the British Pat. No. 919,973 has been built for forming a desired stitch pattern in a predetermined size, wherein representations on the machine frame for displaying each model of such stitch patterns are assorted by colors, and operating positions for regulators to determine the amplitude and feed amount etc. are indicated with those colors. The manually operable knob(s) are operated to the operating position which is indicated with the same color as that of the representation corresponding to the selected stitch pattern. Another type of sewing machine, as stated in the specification and appended drawings of the U.S. Pat. No. 3,871,310, has a ready table indicating operating positions of each manually operable knob suitable to form stitch patterns to be selected.
When, however, the stitch patterns to be selected are in great variety, the indication of such operating positions becomes complex, resulting in embarrassing machine operators contrary to expectation.
In the so-called changeable-cam type sewing machines having no pattern selecting means, still another type of machine is being provided, as stated in the specification and appended drawings of the U.S. Pat. No. 3,807,329, wherein the amplitude regulator and feed regulator, etc. can be, in relation to the inserting operation of a cassette including cams corresponding to the desired stitch pattern into a predetermined position of the machine, automatically set in a suitable condition for the stitch pattern.
In this type of machine, however, cam means for setting the amplitude regulator and feed regulator, etc. must be disposed on a cassette, which necessitates preparing the same number of cassettes as that of stitch patterns. A great deal of time and cost required for preparation of the cams makes this type machine substantially impractical.
In addition, the inconveniences in practice which prevent a machine operator from watching the condition of automatic setting of the machine regulator and feed regulator, etc. and also from changing the setting condition of the regulators by manual operation make the operator skillful in using sewing machines feel unsatisfied.